(a) Technical Field of the Invention
The present invention is related to a pre-casting multi-layer PCB process, and more particularly, to one that allows even thinner circuitry, higher structural strength, lower production cost, and easier production planning.
(b) Description of the Prior Art
In the manufacturing process for the single layer or multi-layer PCB of the prior art, a negative is needed to be exposed for image transfer of the circuitry on a substrate with a copper foil surface, then etched, drilled, and plated; while in case of multi-layer PCB, additional process of high pressure lamination is required. The manufacturing process of the prior art is found with the following flaws:    1. Complicated, consuming too much efforts and time, thus resulting in higher production cost;    2. In the process of lamination, stress from high pressure usually winds up deformed PCB and variations in dimension; and    3. Enormous consumption of materials and size of process facilities to prevent easier production scheduling.
Furthermore, minimum width of the circuitry must be specified in the PCB manufacturing process of the prior art. Otherwise, the circuitry is vulnerable to shortage or interruption, and insufficient strength.